1. Field of the Invention
The invention relates to apparatus for pumping oil wells, and, more particularly, to gas release apparatus for oil well pumps.
2. Description of the Prior Art
Production of oil from oil wells is usually accompanied by some of the gas in the well flowing through the down hole pumps. If this gas is allowed to accumulate in the barrel of the down hole pump, a condition known as "gas lock" occurs. Such a condition occurs when foamy oil or surges of subterranean gases become trapped between the travelling valve fixed to the upper barrel of the downhole pump and the standing valve fixed to the plunger or piston pull tube and seating nipple or shoe of the pump. In such a condition, little if any fluid can be pumped out of the well. The down hole pump may simply be compressing and expanding the gas that is locked in the barrel, Hydrostatic pressure of the column of fluid, when the column is generally several feet in height, bearing on the travelling valve, causing the trapped gases to compress and decompress. This keeps the travelling valve and the standing valve closed preventing the pump from working.
The nature of valves used in existing down hole oil well pumps lends itself to the creation of gas locks. Normally, the pressure differential across the travelling ball valve during the downward stroke opens the valve and allows the fluid in the pump barrel to escape into the discharge tubing. If the fluid in the pump barrel is mostly gas, the travelling ball valve may not open. Thus, as heretofore stated, the pump will not be operating properly and little if any fluid will be flowing into the discharge tubing.
In the past, it has been suggested to remedy such condition by preventing gas from reaching the pump. This was accomplished by using an annulus below the pump inlet. However, in order to implement such a remedy, accurate data is required about the generally unknown formation characteristics. Furthermore, the fluid reservoir characteristic of such formations change with time, requiring constant adjustments to the pump installations. Therefore, the annulus method of preventing gas from reaching the pump is neither practical or effective.
In U.S. Pat. No. 1,676,186 to Hawkins, a valve control for plunger-type pumps is disclosed. However, this arrangement depends on precise spacing of the internal parts which is quite impractical. In U.S. Pat. No. 1,067,312 Conrader, a pump is disclosed for pumping gas. Again, spacing is quite critical and no provision is made to prevent gas lock. Also, such apparatus cannot pump positively on each cycle. In U.S. Pat. No. 1,793,572 to Von Linde, a tubing check valve for a pump is disclosed. Such apparatus is quite expensive and no positive way of unseating the check valve is disclosed. These prior art devices are relatively impractical to implement and are quite costly.
Other approaches to the problems found in oil production have also been patented. None of these however can succeed because they fail to take into full consideration the operating parameters that are present at each and every well.
Goosetree, U.S. Pat. 3,215,085 discloses the lifting of a valve of a valve piston to reduce fluid pounding. He employs a standing valve assembly at the bottom of a pump, which valve assembly has a stationary projection which engages a ball when the plunger descends. His barrel however is not of the travelling variety. Goosetree suffers from the failure to adequately provide a factor for the reality of well operation. He fails to compensate for the fantastic differences in oil well depth which can range into the thousands of feet, among other idiosyncrasies of individual wells by utilizing a fixed design suitable for any and all wells. Thus upon using his device, a well operator would find that there would be times when the rod would not engage the valve member and there would also be times when the travelling valve cage would strike and impact the rod support of the standing valve. Of course it must be born in mind that the pump style of Goosetree is not of the travelling barrel type.
There is thus a need in the industry for travelling barrel type pump that can eliminate the gas lock problem, by allowing dissipation of gas on every single stroke of the pump.